Exemplary embodiments of the invention relate to a drive apparatus for a separator arrangement.
PCT international patent document WO 2007/125066 A1 discloses a separator with a direct drive, the drive apparatus of which features an electric drive motor with a stator and a rotor, or motor rotor, which aligns with the drive spindle. The stator is rigidly connected to the machine frame, and the motor rotor, the drive spindle, the centrifuge drum and the housing form a unit that is elastically supported on the machine frame and oscillates during operation. In this case, the bearing device is arranged between the motor and the drum. The lubricating system of the bearing devices can be accommodated above a partition over the drive motor.
Further examples of separators with direct drive are found in German patent documents DE 10 2007 060 588 A1 and DE 10 2007 061 999 A1, as well as European patent document EP 1 617 952 B2.
German patent document DE 10 2008 059 335 A1 discloses further improvements to the construction and the arrangement of the lubricating system of separators with vertical rotational axis by having the lubricant system for lubricating the bearing arrangement, which is preferably designed as a lubricant circuit, and a lubricant collecting reservoir, wherein the entire lubricant circuit and at least the lubricant collecting reservoir are preferably arranged axially above the motor rotor of the electric drive motor, and wherein lubricant can be fed from the lubricant collecting reservoir directly into the region of the neck bearing, or into the region above the neck bearing, through a lubricant passage formed in or on the housing and extending into the area of the neck bearing, or into the area above the neck bearing, wherein the entire bearing arrangement of the drive spindle is arranged axially above the lower base of the lubricant collecting reservoir.
This constructional form has proved to be inherently successful since it is of a particularly short construction. The spindle, since it is preferably not used for the lubricant circuit, can be used for other tasks such as a product feed, e.g. through a hollow spindle.
For different applications of separators, it is also necessary, however, to design the components so that they can be used in a so-called hazardous area, i.e. the motors are to be of a pressure-tightly encapsulated design, especially based on standard EN 60079 part I or—in countries outside the EU—possibly based on corresponding national standards.
Therefore, there is a requirement for a suitable explosion-proof design of the drive apparatus for the separator or for the creation of an explosion-proof separator drive. The creation of such a drive apparatus is therefore the object of the invention.
In summary, one or a plurality of subsequent advantageous features are realized, common to which is the fact that they advantageously promote or enable the realization of a particularly advantageous drive apparatus of explosion-proof design for separators.
First of all, the drive is preferably realized as a direct drive since this offers the advantage of a compact constructional form so that the design of explosion-proof type is facilitated. The drive spindle by its one end thereby supports the separator drum in a rotation-resistant manner. At the opposite end of the drive spindle, on the other hand, in a preferred embodiment, the rotor of the motor is fastened on the spindle in a rotation-resistant manner.
In this case, the motor housing section—or preferably even only the motor housing section—which accommodates the motor with the stator and the rotor, is especially of a pressure-tightly encapsulated design. The motor housing section preferably only has the stator and the rotor. The construction preferably includes only a single (upper) rotary transmission lead-through between rotating and stationary parts of the drive, which makes it significantly easier to achieve the pressure-tight encapsulation.
Preferably, for ensuring a compact type of construction, the separator bearing arrangement is furthermore located partially, or preferably completely, between the separator drum and the motor, especially the rotor of the motor, wherein the bearing arrangement can consist of two spaced-apart bearing devices at spaced-apart bearing points.
The fact that the motor in a preferred embodiment manages without a separate bearing arrangement and the bearing arrangement of the separator is also used for the pressure-tightly encapsulated motor, is advantageously made possible according to an especially preferred variant by the inclusion of drive parts of the separator in relation to, or in, the pressure-tightly encapsulated space.
The bearing points can be lubricated in a first advantageous variant by means of an oil-circulating lubricating system. As a second advantageous variant, a minimum-quantity lubricating system (with oil droplets injected into the region of the bearings at specified intervals) is a possibility. The bearing housing does not have to be especially encapsulated, although this can be provided since no electrical components are present or accommodated there.
Since with the last-named lubricating variant only a small amount of oil is consumed, the feed into an explosion-proof space is simplified since the passage for injecting the very small amount of oil needs to be only of very small design.
It is also advantageous, in this case compact and simple, if the motor with its motor housing section is flanged on the bearing housing section of the separator. If the motor housing section with the stator and the rotor is of a pressure-tightly encapsulated design in an explosion-proof type of construction, such an encapsulation can again be advantageously dispensed with in the region of the bearing housing section, which simplifies the construction. This is especially made possible in a simple manner when the entire bearing device—and preferably the lubricating system for oil feed and possibly oil discharge—is arranged in/on the bearing housing section above the actual motor or the motor components.
The entire drive is preferably decoupled from the separator frame with regard to vibrations and is furthermore advantageously and simply supported on this by means of elastic spherical bearings.
It is advantageous if the natural frequency of this system is matched to a range of <1300 revolutions per minute, preferably <1100 revolutions per minute. It should especially not lie on a resonance frequency of the system and not lie close to the resonance range either. The operating speed should preferably deviate from these frequencies/rotational speeds by at least +/−5%, especially +/−10%.
It is particularly advantageous if the motor housing section has a cover part vertically towards the top that is adjacent to the rotating part so that the gap is formed between the cover part and the rotating part. In this case, according to a first advantageous variant, the gap is formed between the cover part of the motor housing section and the lubricant collecting reservoir and, according to a second variant which is to be advantageously realized, one of the gaps, or the gap, is formed between the cover part and the drive spindle. The motor can be closed off towards the bottom. The motor housing section, according to a further advantageous embodiment which supplements the advantageous variants of the previous paragraph, is closed off towards the bottom in a simple manner with a preferably detachably fastened cover which, if it is detachable, enables access to the motor on the other side. In this way, the rotary transmission lead-through is to be simply realized on one side only of the encapsulated drive.
An oil catching chamber, in which a feed element for the oil return is attached, is especially preferably also formed between the rotor and the lower rolling bearings of the separator bearing arrangement.
In this case, it is also advantageous for forming an explosion-proof type of construction if the outside diameter of the rotating catching chamber has a defined gap towards the motor housing section, which is dimensioned in such a way that a flashover is prevented in the event of an outward explosion from the interior of the motor. The dimensioning of the gap can be designed according to the invention (narrow and axially of sufficient length) so that despite the gap between rotating and non-rotating parts of the drive an explosion-proof type of construction is possible. The suitable gap dimensions can be determined in a simple test, depending on construction. This determination is necessary since, in contrast to commercially available pressure-tightly encapsulated motors with rolling bearings on both sides of the rotor, influences of the separator drum, especially in the case of unbalances, have to be taken into consideration. As a starting point, however, in this case the standard values of the applicable standards can be applied.
Alternatively (or also additionally, if applicable), this gap, or such a gap, can also be provided at another point, that is to say between the motor housing and the drive spindle or above the bearing device between a ring above the bearing device and the drive spindle.
The motor is preferably a water-cooled motor. Also, a part of the housing is preferably designed as a cooling chamber (preferably with a coolant connection to a cooling circuit) in order to compactly integrate this into the construction. An air-cooled motor, in which the air circulation is created by means of an independent external fan, is conceivable as an alternative. This fan is located beneath the motor outside the housing section. Instead of cooling chambers in the case of the water-cooled motor, the motor then has fins (not shown) for the dissipation of heat.
The stator is preferably arranged directly on the inside circumference of the motor housing section and the rotor is fastened on the outside circumference of the drive spindle in such a way that both the rotor and the stator follow precessional movements of the drum so that during operation the rotor moves radially relative to the stator only as a result of the unbalance and torque influences of the separator drum. Particularly absent up to now in the case of such constructions has been an explosion-proof design which, however, on the transmission lead-through on one side only of the motor housing can still be realized with a narrowly dimensioned gap. The entire unit (having at least the motor with stator and rotor and the motor housing section) is supported on a machine frame by means of elastic elements via the flange region.
The rotor of the motor is preferably fastened on the spindle in a simple manner by means of a screw clamp. In this case, the rotor can be drawn against a spindle collar, for example.
Alternatively, an overall interconnection can also be created, however, by the rotor being clamped against the oil catching chamber which is guided on the spindle and against at least the lower rolling bearing. In this case, a spindle collar above this rolling bearing constitutes the stop. Clamped in this context means an interconnection of the parts produced by screwing down tight.
The motor housing is especially advantageously designed in a pressure-tightly encapsulated type of construction so that it withstands an explosion pressure in the interior of the motor of a minimum of 10 bar, especially of a minimum of 15 bar. In special cases, the housing can also be designed so that it withstands a pressure of a minimum of 20 or even 30 bar.
The cover, as the lower termination of the drive housing, is preferably provided with long gaps towards the housing so that a flashover in the event of an explosion in the interior of the motor is excluded (not shown).
The rolling bearing arrangement of the separator is preferably designed so that it cannot be displaced upwards in the event of an explosion in the interior of the motor. A possible limitation of the distance is effected by means of a ring above the neck bearing. Alternatively, use is preferably made of rolling bearings having no clearance, or only a small clearance, in the axial direction.
Created as a most advantageous variant is such an explosion-proof motor housing, with motor, which can be of an explosion-proof design without the bearings and also the lubricating system having to be positioned in the interior of the pressure-tightly encapsulated area.
One reason—which is why such constructions have not been developed up to now—is the governing of the frequency matching of the elastic coupling to the machine frame which as a result of the higher mass of a commercially available explosion-proof motor is of a more complicated and more unfavorable design than with light standard motors. Furthermore, the dimensioning of the gap between rotating and stationary parts of the drive and the matching of the drive components involved are to be governed by the separator-specific influences.
A second reason is that for such applications there were previously inertized drives that by means of external, additional devices ensured safety in hazardous areas by means of a positively pressurized encapsulation with inert gas. As a result of the new drive, additional devices are dispensed with.
A further aspect is the gap and the gap length against a spark ignition in the event of an explosion. The necessary development of a precise control, another configuration, and the necessary tests have been avoided up to now in the case of separator drives.
Furthermore, up to now the rolling bearings on both sides of the rotor have always been a component part of the motor, moreover, in the case of known, pressure-tightly encapsulated motors for the hazardous area.